There is too much on the page. It makes it difficult to focus on anything. I guess your site is trying to sell one particular thing to a visitor. Make that one thing the focus of the layout. You can have other things on the page but they should be as invisible as possible and help your main 'thing' stand out.

It's a nice layout but I would recomend some changes. Try not to use the most common font font such as Times New Roman and pick something better looking, for example Arial or Verdana or maybe even some font that is not included in Windows XP (you can find amazing fonts anywhere on internet for free). I also don't like a lot a pink part, it's a little bit annoying to look at. Try picking some lighter color.
I like the design a lot, it's very well structured, just change some colours and fonts and it will be perfect.

You have used many colors but on the menu bar you have a blue and on the footer another different blue, it's not very beautiful...
I think it would be better if you keep the same blue and gray colors you have set in the footer.

The location of the banner advert is standard enough. However, it will be nice if it displays an extension of your logo in the top-left, with a tagline or some such. You can fade it out to display the banner, and the banner can fade out to display the extended header, and so on and so forth, for ever. To get the fade-in/fade-out effect, you could use jquery as shown in the tutorial here.

In the main body, as has been pointed out, the layout doesn't emphatically/clearly convey what the website is about. Is it a news/magazine like site that collects and displays articles? Is it a personal blog? If you want people to opt-in, and this is your idea of a landing page for your subscription box, then it's badly done because the subscription page is overshadowed by all the other stuff on the page. I'm not sure what the box in pink is supposed to be - a page on your own site, or an advert? Consider a narrower sidebar if these aren't your main focus.

I'd like the "Welcome to..." text to be the first thing that hits me. I don't want to be looking/scrolling for it. But again, this is just me

You have an overwhelming footer. Consider the footer area in the layout here (scroll all the way to the end - and check out some of the other templates at this site too, for this kind of a footer-area), and try to mimic it for achieving the same effect but with greater style.

I agree with the comment about the color scheme, it looks a bit patchy/pieced-together, and a more coherent/co-ordinated look would be more appealing.

Of course, much of the above was subjective, and no offense intended! You have a nice start, keep at it. Good luck!